The invention relates to an appliance having a first and a second housing shell, each shell being provided with a closed circumferential contact rim having a wall portion corresponding with the respective other one, which wall portions in the mounted state of the housing shells are connected to one another with a sealing element interposed therebetween, said sealing element being integral with a wall of the wall portion of the first housing shell, while the housing shells are fastened to one another by fastening means under the influence of a fastening force in a fastening direction with the sealing element interposed therebetween.
To make appliances having two housing shells watertight, seals are often used nowadays which are fastened to a wall portion of the contact rim of one of the housing shells by means of a two-component injection-molding method. The advantage of such seals simultaneously made during injection molding is that separate seals, whose mounting is time-consuming, need no longer be used. An injection-molded seal is already in the correct location, so that assembly can take place quicker. Loose seals have to achieve a good sealing at both housing shells. If the seals are injection-molded, the good sealing to one housing shell is already assured. During mounting, the housing shells are connected to one another by fastening means, for example a screw connection, whereby the seal is achieved at the same time. The sealing force is dependent here on the force with which the housing shells are connected to one another, for example are screwed together. To obtain as good as possible a seal, the housing shells are interconnected as tightly as possible. This often leads to undesirable stresses in the housing shells, especially if the material of the housing shells is a synthetic resin. The sealing must be achieved along the entire contact rim, whereas the fastening is present in a single location only. The risk of deformation of the housing shells, especially in the course of time, is increased thereby, and thus the risk that the sealing will no longer be satisfactory in certain locations.
It is an object of the invention to obtain a sealing of the housing shells which is reliable over a longer period of time in an appliance which has two housing shells.
The appliance according to the invention is for this purpose characterized in that, after mounting of the housing shells, a sealing is created between the sealing element and a wall of the wall portion of the second housing shell wherein the direction of the sealing force is approximately perpendicular to the direction of the fastening force, and the sealing force is substantially independent of the fastening force.
This type of sealing has the result that the seal is fully created after the housing shells have been placed against one another and before the housing shells have been interconnected by the fastening means. The fastening means have no adverse effects on the seal, not even after a long period of time. The dimensional tolerances for the housing shells are less critical than in existing appliances in which the tolerances directly influence the degree of sealing.
Preferably, the sealing element is provided with a pointed projection extending substantially perpendicularly to the fastening direction, seen in cross-section in the unmounted state of the housing shells. The pointed projection of the sealing element ensures as it were that an edge seal arises. When the housing shells are placed against one another, the extremity of the projection of the sealing element, seen in cross-section, is pressed against the opposed wall portion, whereby a better seal is obtained. The pointed projection does not constitute a problem during unmolding because the sealing element is made of a soft material.
An embodiment of the appliance is characterized in that the contact rim of the second housing shell is provided with a groove in which the sealing element abuts against two mutually opposed walls of the groove in the mounted state of the housing shells.
Another embodiment of the appliance is characterized in that the contact rim of the second housing shell is provided with a groove in which one of the walls of the groove abuts against the sealing element and the opposed wall portion of the groove abuts against a wall of the wall portion of the first housing shell in the mounted state of the housing shells. Mounting becomes easier as a result of this because the wall portions, which are made of a harder material, easily slide along each other. A further embodiment thereof is characterized in that the wall portion of the first housing shell is elongate and extends in the fastening direction, while the wall against which the sealing element is fastened extends substantially in the fastening direction. It is possible that the soft material of the sealing element starts stripping off during mounting of the housing shells. The elongate dimension of the wall portion and the fact that the sealing element extends over the entire wall imply that the sealing element is upset in the sealing direction during assembling together of the housing shells and at the same time is elongated in the mounting direction, transverse to the sealing direction. This facilitates the assembly.
A further embodiment is characterized in that the first housing shell is provided with a groove, and one of the walls of said groove is provided with the sealing element, while the wall portion of the second housing shell lies enclosed between the sealing element and the wall of the groove opposed to the sealing element in the mounted state of the housing shells.